This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for METHOD FOR CONTROLLING A SYSTEM OF AUTOMATIC GUIDED VEHICLES earlier filed in the Korean Industrial Property Office on the 4th of November 1999 and there duly assigned Ser. No. 99-48563.
1. Field of the Invention
The present invention relates to a method for controlling an Automatic Guided Vehicle system (AGV system), and more particularly, to a method for controlling an AGV system capable of efficiently controlling a plurality of automatic guided vehicles.
2. Description of the Related Art
Generally, with reference to FIG. 1, an AGV system such as an automatic assembly line, etc., includes a plurality of automatic guided vehicles 20, and a central controller 10 for controlling the movement and performance of the automatic guided vehicles 20. Wireless communicators 12 and 21 are provided between the automatic guided vehicles 20 and the central controller 10 for intercommunication therebetween. Accordingly, the control method includes a control method of the central controller 10, and a control method of the automatic guided vehicles 20.
After checking the status of the whole system, the central controller 10 sends out operation commands to the respective automatic guided vehicles 20 through the wireless communicator 12 in a certain communication format. Each automatic guided vehicle 20 receives the commands from the central controller 10 through another wireless communicator 21. According to the command it received, the automatic guided vehicle 20 moves along a requested guidepath 27, or stops at a requested workstation 25 to load/unload parts, materials, or products, or to perform a charging process.
As shown in the flowchart of FIG. 2, the method of the central controller 10 for controlling the automatic guided vehicles 20 includes the steps of: sending out a new command to the automatic guided vehicle 20 for moving or loading/unloading (Step S41); and checking the completion of the command sent to the automatic guided vehicle 20 (Step S42). When determining the completion of the command at the automatic guided vehicle 20, a new command is analyzed and the steps of sending out new commands, and checking the completion of each new command (S41 and S42) are repeated.
When the automatic guided vehicle 20 receives a command from the central controller 10, the automatic guided vehicle 20 moves to a newly requested location to perform the loading/unloading of parts and completes the command it received, and reports the completion of the command to the central controller 10.
More specifically, the control method of the automatic guided vehicles 20 includes the steps of: receiving the command transmitted by the central controller 10; command performance by the automatic guided vehicles 20; reporting command completion by the automatic guided vehicles 20; reception of the command completion report by the central controller 10; and transmission of a new command by the central controller 10.
According to the conventional control method, since the central controller 10 transmits a new command only after the central controller 10 receives the previous command completion report from the automatic guided vehicle 20, communication time is consumed for reporting the command completion and receiving a new command at the automatic guided vehicle 20 between each task.
Further, since it takes time for the automatic guided vehicle 20 to analyze the command received from the central controller 10 and convert the command to an appropriate form, the command cannot be directly carried out by the automatic guided vehicle 20 when the automatic guided vehicle 20 receives the command from the central controller 10.
When the central controller 10 controls a plurality of automatic guided vehicles 20 simultaneously, in particular, sometimes it takes a lengthy time for the central controller 10 to analyze the commands for the automatic guided vehicles 20, and thus the central controller 10 keeps the automatic guided vehicles 20 waiting for the new commands, thereby lengthening the communication time for the automatic guided vehicles 20.
Here, due to a need for communication time and command analyzing time between performance of each command given to the automatic guided vehicles 20, the conventional control system had an operational efficiency problem.
The present invention has been developed to overcome the above-mentioned problems of the related art, and accordingly, it is an object of the present invention to provide a method for controlling an AGV system having a central controller that sends out a new command to an automatic guided vehicle which is performing the command it previously received from the central controller, the method being capable of reducing communication time and command analyzing time between the respective command performances of the automatic guided vehicles thus improving the operational efficiency.
The above object is accomplished by a method for controlling an AGV system having a plurality of automatic guided vehicles and a central controller for controlling the automatic guided vehicles according to the present invention, including the steps of: (a) transmitting an IMMEDIATE command from the central controller to the automatic guided vehicle; (b) checking by the central controller as to whether the automatic guided vehicle, which is performing the IMMEDIATE command, can receive a NEXT command; (c) transmitting the NEXT command by the central controller to the automatic guided vehicle; (d) continuously receiving, analyzing, and storing of the NEXT command by the automatic guided vehicle while the automatic guided vehicle receives and performs the IMMEDIATE command; and (e) sequentially performing NEXT commands stored in the automatic guided vehicle after completion of the IMMEDIATE command.
Step (b) includes the steps of: checking by the central controller as to whether there is a NEXT command to send out to the automatic guided vehicle; and checking by the central controller as to whether the automatic guided vehicle can receive the NEXT command. This is followed by step (c) of transmitting of the NEXT command by the central controller to the automatic guided vehicle.
Further, step (b) includes the steps of: receiving of the NEXT command by the automatic guided vehicle from the central controller; analyzing and converting of the NEXT command into an execution command of the automatic guided vehicle; and storing of the converted NEXT command by the automatic guided vehicle into a buffer of the automatic guided vehicle.
In the control method of the AGV system according to the present invention, since the receiving and analyzing of the command by the automatic guided vehicle are carried out during the performance of the command that the automatic guided vehicle has previously received from the central controller, communication time and command analyzing time of the central controller and the automatic guided vehicle can be saved. Accordingly, the operational efficiency of the AGV system is improved.